Reader for a facsimile apparatus

Abstract: A reader for a facsimile apparatus comprises a line buffer capable of storing at least one line of read raw data and an image buffer for storing encoded image data, for reading an image in synchronism with a line sync signal. The image is continuously read at a period of the line sync signal until the image buffer becomes full, and after the image buffer has become full, the image is read at a period of at least two line sync signals, and when a vacent area of the image buffer subsequently exceeds a predetermined volume, the image is again read continuously at the period of the line sync signal.

Description: The present invention relates to a reading method for a reading apparatus. From EP-A-0 212 487 is known a method for controlling vertical scan speed when a document in a recording medium is moved in a vertical scanning direction to read the document and record signals on the recording medium. The reading signals are stored in the line buffer memory and code signals corresponding to the read signals in a code buffer memory. It is proposed there to change over a high speed vertical scan mode with hysteresis to a low speed vertical scan mode and vice versa in accordance with the number of buffered code bits in the code buffer memory to read the document and record the signals on the recording medium. From US 4,160,279 is known a reading apparatus in which an optical system scans an original document and produces quantisized electrical signals which are stored in a buffer memory. A data compression unit reads out the signals and performs data compression thereon asynchronously with storage of the signals in the buffer memory. The data compression rate decreases in accordance with the proportion of high density areas of the document, and the electrical data signals accumulate in the buffer memory. The scanning speed is automatically decreased as the amount of signals in the buffer memory increases so that the scanning speed is controlled to correspond to the data compression rate. From the patent abstract of the Japanese publication JP 3219764 is known a scanning control system for use in a transmission or reception system of a facsimile equipment for controlling the secondary speed of a image reader or recorder provided therein. In the transmission system the scanning control system is coupled to an image memory for storing image information inputted from the image reader and supplying the image information to a coder, and responsive to the input signal and output signal of the image memory so as to detect the remaining capacity of the image memory. The scanning control system controls the secondary scanning speed in accordance with the detection results of the remaining capacity of the image memory. The secondary scanning speed is continuously increased under a condition of limiting it to a predetermined maximum speed when the remaining capacity is in a first range, maintained as it is when being in a second range, continuously decreased under a condition of limiting it to a predetermined intermediate speed when being in a third range and the secondary scanning is stopped when being in a fourth range. In restarting after the stopping, the secondary scanning speed is set to a predetermined minimum speed. From US 4,628,368 is known a method of controlling the sub-scanning of a document reading apparatus. The speed, acceleration, or deceleration of the reading section is controlled according to the amount of information stored in a buffer memory which temporarily stores information read by the reading section. The values of the movement speeds, accelerations and decelerations are predetermined according to the stored information amount of the buffer memory and the time of controlling the reading section, one of these values is selected according to the currently stored information amount of the buffer memory. Whereby any vibration in the reading section is prevented to eliminate the irregularity in the sub scanning of the reading section. In a prior art facsimile apparatus, read image data is transmitted in the following manner. As shown in Fig. 2, a plurality of line buffers each capable of storing one line of raw data (non-coded data) are provided and data read by a CCD is binarized and transferred to the line buffers. When one line of data is stored in the line buffer, it is transferred to an encoder, encoded thereby and stored in an image buffer. The data stored in the image buffer is sequentially read and sent to a modem. In the prior art read control, a line sync signal determined by a storage time of the CCD is used as a reference, and if the line buffer is vacant (or free) when the line sync signal is applied, an image is read and a document sheet is fed, and if the line buffer is full, the reading is not carried out but it waits until the line buffer becomes vacant. Accordingly, the operation of the read system depends on the complexity of the document sheet image and a communication rate. For a simple image, a data compression rate is high and the image can be transmitted at a high rate and it is rare that the line buffer becomes full. Thus, the image can be continuously read at a substantially constant speed. For a complex image, the data compression rate is low and a transmission bit rate cannot follow a generation speed of one line of encoded data. Thus, the image buffer becomes full and the line buffer becomes full and the operation is intermittent. In a worst case, the intermittent operation is such that each time one line is read, the vacant state of the line buffer is waited before the next line is read. Fig. 3 shows the movement of a document sheet feed roller when a drive trigger is outputted to a document sheet feed stepping motor. As stated above, the read operation depends on the document sheet. Even if the drive trigger is outputted to the document sheet feed stepping motor as shown in Fig. 3, there is a delay before the document sheet feed roller is actually moved. Further, since the read operation of the image and the output of the drive trigger are synchronized, if a plurality of lines are to be continuously read, the first line and the second line read substantially same area. Fig. 4 shows the movement of the document sheet feed roller in the intermittent reading by every other line. Since there is still a delay to the drive trigger before the feed roller is actually moved, the document sheet feed roller is rotated by two lines after it has read the substantially same area in the first line and the second line. Thus, when the intermittent reading by a small number of lines is effected, the linear image reading is not attained and the image disturbed. It is an object of the present invention to provide a reading method for a reading apparatus which carries out the read operation in accordance with a vacant capacity of a buffer. It is a still another object of the present invention to provide a reading method for a reading apparatus which selects an intermittent operation or a continuous operation of relative movement between a document sheet and a line sensor depending on a vacant capacity of a line buffer. Fig. 1 shows a block diagram of an embodiment of the present invention, Fig. 2 shows a data flow chart of image data, Fig. 3 shows the movement of a shaft of a document sheet feed roller when motor trigger is continuously applied, Fig. 4 shows the movement of the shaft of the document sheet feed roller in an intermittent operation with every other line, Fig. 5 shows a flow chart of control in the embodiment, and Fig. 6 shows a flow chart of control in other embodiment of the present invention. Fig. 1 shows a block diagram of an embodiment. Numeral 1 denotes a control unit, numeral 2 denotes an image read unit for reading a document sheet, photo-electrically converting it and converting it to black and white binary data, numeral 5 denotes a clock generator for generating a line sync singal determined by a storage time of a photo-electric conversion element included in the read unit 2, numeral 6 denotes a signal line for the line sync signal, numeral 7 denotes a line buffer capable of storing a plurality of lines of raw data (non-coded data), numeral 8 denotes an encoder for encoding the raw data stored in the line buffer 7, numeral 9 denotes an image buffer for storing the data encoded by the encoder 8, numeral 10 denotes a modem for transmitting the data stored in the image buffer 9, numeral 11 denotes an NCU, numeral 12 denotes a motor drive unit for driving a motor by a command from the control unit, and numeral 13 denotes a read motor for feeding a document sheet to be read. A time required to encode one line is within an interval of the line sync signal. The binary image data converted to the electrical signal by the image read unit 2 is stored in the line buffer 7, and when one line of image data is stored in the line buffer 7, the image data is transferred to the encoder 8 and encoded thereby and stored in the image buffer 9. The data stored in the image buffer 9 is sequentially read, modulated by the modem 10 and transmitted. When the line sync signal is applied and the line buffer 7 is vacant, the control unit 1 transfers the image data to the line buffer 7 and commands to the motor drive unit 12 to advance the read motor 13 by one line. Namely, until the image buffer 9 becomes full, the continuous read operation is-carried out in synchronism with the line sync signal. When the image buffer 9 becomes full and the line buffer 7 also becomes full, the read operation is not carried out even if the line sync signal is applied but it waits until the line buffer 7 becomes vacant. Even if the line buffer 7 subsequently becomes vacant, the continuous reading is not effected but the next line is read with the interval of at least one line sync signal. Thus, after the image buffer 9 has become full, the intermittent reading with every other line is carried out. When the data rate transmitted by the modem 10 becomes faster than the generation rate of the encoded data so that the vacant area of the image buffer increases above a predetermined volume, the continuous image reading is carried out until the image buffer 9 again becomes full. By this control, the read operation can be limited to the continuous reading and the intermittent reading with every other line and the linear image reading is attained without affecting to the communication time. Fig. 5 shows a flow chart of the read control. When the image reading is started, the control unit 1 waits for the input of the line sync signal in a step S101. When the line sync signal is applied, the process proceeds to step S102 to determine if there is a vacant area in the line buffer 7 or not. If there is, the process proceeds to a step S103 to determine whether a flag FLAG1 which indicates whether to read or not is "0" or not. If it is "0", the process proceeds to a step S104 to read one line, and a command is issued to the motor drive unit 12 to advance the motor 13 by one line in a step S105. In a step S106, whether a flag FLAG0 which indicates whether the image buffer 9 is full or not is "1" or not, and if it is not "1", the process proceeds to a step S107 to determine if one page of reading has been completed or not. If it has not, the process returns to the step S101 to read the next line. If the line buffer 7 is not vacant in the step S102, the process proceeds to a step S108 to set the FLAG0 to "1" assuming that the image buffer 9 has become full. This is due to the fact that the time required to encode one line is shorter than the line sync signal interval. The process then returns to the step S101 to wait for the vacant state of the line buffer 7. When the line buffer 7 becomes vacant, the process proceeds to a step S103. In the step S103, if the FLAG1 is "1", the reading is not effected and the process proceeds to a step S109 to reset the FLAG1 and returns to the step S101. If the FLAG0 is "1" in the step S106, the process proceeds to a step S110 to determine if the vacant area of the image buffer 9 is above the predetermined volume or not, and if it is not, the process proceeds to a step S111 to set the FLAG1 to "1" to continue the intermittent reading and then proceeds to the step S107. If the vacant area of the buffer 9 is above the predetermined volume in the step S110, the FLAG0 and the FLAG1 are reset in steps S112 and S113 to stop the intermittent reading. By this control, the continuous reading is effected until the image buffer 9 becomes full, and after the image buffer 9 has become full, the intermittent reading with every other line is effected until the vacant area of the image buffer 9 reaches the predetermined volume. When the vacant area of the image buffer 9 exceeds the predetermined volume, the continuous reading is reinitiated so that the linear image reading is attained without affecting to the communication time. (Other embodiments) In the above embodiment, the interval of the intermittent reading is one line sync signal interval. Alternatively, the reading interval may be a plurality of line sync signal intervals such as three or four depending on a damping characteristic of the motor. Fig. 6 shows a flow chart when the interval is N (N=1, 2, 3, ..) line sync signal intervals, and the control therefor is explained below. Fig. 6 shows a flow chart of the read control when the one line read interval is extended for the intermittent reading with every other line. The control unit 1 waits for the input of the line sync signal in a step S201. When the line sync signal is applied, the process proceeds to a step S202 to determine if the FLAG0 which indicates whether the image buffer 9 has become full is "1" or not. If it is not "1", the process proceeds to a step S203 to determine if the line buffer 7 is vacant or not. If it is vacant, the process proceeds to a step S204 to conduct the one line read, and in a step S205, a command is issued to the motor drive unit 12 to advance the motor 13 by one line. In a step S206, whether the FLAG0 is "1" or not is determined, and if it is not "1", the process proceeds to a step S207 to determine if it is the end of one page or not. If it is not the end, the process returns to the step S201 to read the next line. If the FLAG0 is "1" in the step S202, the process proceeds to a step S208 to increment the counter. The process then proceeds to a step S209 to compare the count of the counter with a predetermined count N. If it is not equal, the reading is not effected and the process returns to the step S201. If it is equal to N, the counter is reset in a step S210 and the process proceeds to the step S203. If the line buffer 7 is not vacant in the step S203, the process proceeds to a step S211 assuming that the image buffer 9 is full to set the FLAG0 to "1". Then, the process returns to the step S201. If the FLAG0 is "1" in the step S206, the process proceeds to a step S212 to determine if the vacant area of the image buffer 9 is above the predetermined volume or not. If it is not, the process proceeds to the step S207. If it is above the predetermined volume, the process proceeds to a step S213 to reset the FLAG0 to stop the intermittent reading, and the process proceeds to the step S207. By this control, the interval of the line reading in the intermittent reading is at least N line sync signal intervals so that the control may fit to the damping characteristic of the motor. In accordance with the present invention, the read operation is limited to the continuous operation and the intermittent operation with every other line so that the intermittent operation with a small number of lines (2 to 4 lines) is eliminated and the linear image reading is attained. When the vacant area of the image buffer exceeds the predetermined volume during the intermittent reading with every other line, the continuous reading is reinitiated. Accordingly, the linear image reading is attained without affecting the communication time. A reader for a facsimile apparatus comprises a line buffer capable of storing at least one line of read raw data and an image buffer for storing encoded image data, for reading an image in synchronism with a line sync signal. The image is continuously read at a period of the line sync signal until the image buffer becomes full, and after the image buffer has become full, the image is read at a period of at least two line sync signals, and when a vacent area of the image buffer subsequently exceeds a predetermined volume, the image is again read continuously at the period of the line sync signal.

Claims: A reading method for a reading apparatus having an image memory for storing image data, the reading apparatus reading an image and performing relative movement concerning a document sheet and a reading sensor (2) in synchronism with a line sync signal, wherein said reading apparatus includes encoding means (8) for encoding image data and said image memory includes a line buffer (7) and an image buffer (9), and wherein said encoding means encodes image data stored in the line buffer and stores the encoded image data in the image buffer, said method comprising the steps of continuously performing the relative movement to read the image at a period of the line sync signal, until the line buffer becomes full, performing intermittently the relative movement to intermittently read the image after the line buffer has become full, said relative movement being performed for one line once per at least two line sync signals; and again continuously performing the relative movement to read the image when a vacant area of the image buffer subsequently exceeds a predetermined volume, at the period of the line sync signal, wherein said predetermined volume is set to be different from a full capacity of the image buffer so that the continuous relative movement is not performed before the vacant area of the image buffer is substantially greater than zero after the image buffer has become full. A reading method for a reading apparatus according to claim 1 wherein when a time corresponding to k line sync signals is required to read one line, the image is read at a period corresponding to k line sync signals until the image buffer becomes full, and after the image buffer has become full, the image is read at a period corresponding to at least k+1 line sync signals, and when the vacant area of the image buffer subsequently exceeds the predetermined volume, the image is read at the period corresponding to k line sync signals. A reading method for a reading apparatus according to claim 1 or 2, the reading apparatus further comprising clock means (5) for generating a line sync signal of a predetermined period; feed means (13) for feeding a document sheet in synchronism with said line sync signal; communication means (10) for sending the image signal stored in said image buffer to an external line; and control means (1) for supplying a drive pulse to said feed means to feed the document sheet by one line for every N input pulses of said line sync signal when a vacant area of said image buffer is below a predetermined volume and reading the image signal output from said reading sensor in synchronism with a second drive pulse after the output of a first drive pulse. A reading method for a reading apparatus according to Claim 3, wherein the number N of pulses of said line sync signal counted by said control means is an integer not smaller than 2. A reading method for a reading apparatus according to Claim 3, wherein said control means supplies the drive pulse each time the line sync signal is generated and reads the image signal output from said reading sensor when the vacant area of said image buffer exceeds a predetermined volume.

Inventors: ONO TAKASHI, ONO, TAKASHI, ONO, TAKASHI, C/O CANON KABUSHIKI KAISHA
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1994
Main classification: H04N1
IPC codes: H04N1, G06T1